The overall objectives of this project are to evaluate the role of a myocardial depressant factor (MDF) in the pathophysiology of circulatory shock. This can be classified into five major separate goals. These are to determine the overall goal: a. Chemical identity of MDF. b. Actions of MDF and related substances on the circulatory system. c. Mechanism of formation and transport of MDF to the circulation. d. Mechanism of inactivation and clearance of MDF. e. Contribution of MDF to lethality in various types of circulatory shock.